The position of a mobile station, such as, for example, a cellular telephone, may be estimated based on information gathered from various systems. One such system may comprise the Global Positioning System (GPS), which is one example of a satellite positioning system (SPS). SPS systems such as GPS may comprise a number of space vehicles (SV) orbiting the earth. Another example of a system that may provide a basis for estimating the position of a mobile station is a cellular communication system comprising a number of terrestrial base stations to support communications for a number of mobile stations.
A position estimate, which may also be referred to as a position “fix”, for a mobile station may be obtained based at least in part on distances or ranges from the mobile station to one or more transmitters, and also based at least in part on the locations of the one or more transmitters. Such transmitters may comprise SVs in the case of an SPS and/or terrestrial base stations in the case of a cellular communications system, for example. Ranges to the transmitters may be estimated based on signals transmitted by the transmitters and received at the mobile station. The location of the transmitters may be ascertained, in at least some cases, based on the identities of the transmitters, and the identities of the transmitters may be ascertained from signals received from the transmitters.
An almanac may be maintained for systems used for position estimation. The almanac may contain various types of information, including, for example, information that may be used in position estimation operations. Such information may include the identities and locations of the various transmitters of the system, for example. However, in some situations, a network operator may decide to change or renumber its mobile network code, change or renumber one or more local area code(s) associated with the mobile network code, change or renumber one or more base station identifier associated with a local area code. These changes in mobile network code, local area code, and base station identifiers can adversely impact the accuracy of the WWAN almanac, and which in turn may adversely impact the accuracy of position fix generated based on the WWAN almanac.
Therefore, it is desirable to have method, apparatus and system for monitoring and maintaining integrity of WWAN almanac.